Strap securing structure of footwear article

ABSTRACT

An article of sandal includes a sole structure and a strap secured on the sole structure. The sole structure has an upper surface and a lower surface and an aperture penetrating through the sole structure and exposing an engaging surface between the upper surface and the lower surface of the sole structure. The strap is secured on the upper surface of the sole structure by having a joining plug assembled in the aperture. The joining plug has a blocking portion and a pillar portion connected to a top surface of the blocking portion. The top surface of the blocking portion has a plurality of protrusions that are in direct contact with the engaging surface of the sole structure.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention generally related to a footwear article, and moreparticularly related to a strap securing structure of a sandal.

2. Description of the Prior Art

A sandal is a type of footwear usually includes a strap secured on asole structure to provide a room for accommodating the foot andretaining the sandal on the foot of the wearer. The sole structure ofthe sandal is therefore positioned between the foot and the ground toprotect the foot from directly contacting the ground and also attenuateground reaction force and lessen stresses the foot and leg bearingduring walking, running and other ambulatory activities. Due to theseadvantages such as easy to wear, quick drying, simple structure and easyto clean, sandals have been widely used by people in their daily lives,especially in the occasions need temporary wearing, such as in thehospital, in the hotel or at the beach.

The flip-flop is a kind of sandal including a Y-shaped strap secured tothe sole structure. Typically, the Y-shaped strap of a flip-flop usuallyincludes a toe post secured to a fore portion of the sole structurecorresponding to the position between the big toe and the next toe ofthe foot and two sidebands joined at the toe post, extended oppositelyand secured to the two side portions of the sole structure respectivelycorresponding to the inner arch and the outer arch of the foot. Oneconventional method to secure the Y-shaped strap to the sole structureis by inserting the joining plugs formed at the terminals of theY-shaped strap through the corresponding apertures in the sole structureand using the apertures to obstructing the joining plugs from beingpulled back.

To provide better wearing comfort and reduce manufacturing cost, thestrap and the sole structure are usually formed from elastic or flexibleplastic materials which are easy to produce in mass production, such asethylene vinyl acetate (EVA), rubber, polyvinyl chloride (PVC) orthermoplastic polyester elastomer (TPE). However, the elasticity andflexibility of the plastic materials may adversely result in deformationof the joining plugs of the strap and/or the apertures of the sole whilebeing stressed during the activity of the wearer. This may result inunexpected disassembly of the strap and the sole structure and may causethe wearer to fall down during activity. Therefore, there is still aneed in the field to provide an improved strap securing structure whichmay avoid the aforesaid problem.

SUMMARY OF THE INVENTION

In light of the above, the present invention is directed to provide astrap securing structure of a sandal which may avoid the aforesaidproblem. The trap securing structure according to the present inventionmay better secure the strap to the sole structure and be formedintegrally with the strap without increasing the manufacturingcomplicity. The wearing comfort and stability may be simultaneouslyguaranteed.

According to an embodiment, an article of sandal is disclosed. Thearticle of sandal includes a sole structure having an upper surface anda lower surface and an aperture penetrating through the sole structureand exposing an engaging surface between the upper surface and the lowersurface of the sole structure. A strap is secured on the upper surfaceof the sole structure by a joining plug thereof assembled in theaperture. The joining plug has a widened blocking portion and a pillarportion connected to a top surface of the blocking portion. The topsurface of the blocking portion has a plurality of protrusions that arein direct contact with the engaging surface of the sole structure.

It is one feature of the present invention that by forming a pluralityof protrusions on the top surface of the blocking portion that are indirect contact with the engaging surface of the sole structure, thefriction between the top surface of the blocking portion of the joiningplug and the engaging surface of the sole structure may be increased,which may prevent the joining plug from being disassembled from theaperture of the sole structure while being forced to pull away from theupper surface of the sole structure during the activity of the wearer. Abetter secured assembly of the strap and the sole structure is thereforeobtained. Furthermore, the joining plug having protrusions may beintegrally formed with other portions of the straps without increasingthe cost and complexity of the manufacturing process.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following description, embodiments of the present invention willbe explained on the basis of the drawings, in which:

FIG. 1 is a perspective view of a flip-flop according to an embodimentof the present invention;

FIG. 2 is an exploded perspective view of a flip-flop according to anembodiment of the present invention;

FIG. 3 is an enlarged perspective view of a joining plug of a strap of aflip-flop according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a sole structure of a flip-flopaccording to an embodiment of the present invention, wherein the upperportion of FIG. 4 is a perspective bottom view of the sole structure,and the lower portion of FIG. 4 is a cross-section view of an apertureof the sole structure along the line A-A′ shown in the upper portion ofFIG. 4;

FIG. 5 and FIG. 5A are a schematic cross-section diagrams respectivelyshowing the assembly of a joining plug and an aperture of a solestructure of a flip-flop according to an embodiment of the presentinvention; and

FIG. 6 shows some modifications of the joining plug of as shown in FIG.3.

DETAILED DESCRIPTION

To provide a better understanding of the present invention to those ofordinary skill in the art, several exemplary embodiments of the presentinvention will be detailed as follows, with reference to theaccompanying drawings using numbered elements to elaborate the contentsand effects to be achieved. The accompanying drawings are included toprovide a further understanding of the embodiments, and are incorporatedin and constitute a part of this specification. These embodiments aredescribed in sufficient detail to enable those skilled in the art topractice the invention. Other embodiments may be utilized and thatstructural, logical and electrical changes may be made without departingfrom the spirit and scope of the present invention.

The invention will now be described with reference to the followingnon-limiting example. In the following description, embodiments of aflip flop type sandal including a Y-shaped strap secured to a solestructure are explanatorily illustrated to show the features of thepresent invention. It should be understood that the present inventionmay be applied in other types of footwear, such as one-piece typesandals or other types of sandals. The present application may be alsoused to secure other footwear components to the sole structures.

Please refer to FIG. 1 and FIG. 2. FIG. 1 is a perspective view of aflip-flop according to an embodiment of the present invention. FIG. 2 isan exploded perspective view of the flip-flop as shown in FIG. 1. Asshown in FIG. 1, the sandal 10 is a flip-flop type sandal formed byassembling a sole structure 12 and a Y-shaped strap 20. The solestructure 12 may be a flat sheet piece having a uniform thickness. Thesole structure 12 includes an upper surface 14 and a lower surface 16opposite to the upper surface. The upper surface 14 receives thewearer's foot thereon and the lower surface 16 contacts the ground whenthe sandal 10 is worn on a foot. Optionally, the upper surface 14 andthe lower surface 16 may respectively have designed patterns or textures(not shown in the diagrams) for wearing comfort, providing appearance orfunctionality. The strap 20 is attached to the sole structure 12 on theupper surface 14 and configured to provide a room for receiving foot andattaching the flip-flop to the foot of the wearer. According to anembodiment, as shown in FIG. 1, the strap 20 includes a toe post 22 andtwo sidebands 24. The toe post 22 is secured to a fore region 12 a ofthe sole structure 12 and would be disposed between the big toe and theadjacent toe of the foot. The two sidebands 24 are joined at the toepost 22 and extend oppositely toward the two side portions 12 b of thesole structure 12, respectively correspond to the inner arch and theouter arch of the foot. As shown in FIG. 2, the terminals of the toepost 22 and the two sidebands 24 respectively have a joining plug 26.The strap 20 is secured to the sole structure 16 by inserting thejoining plugs 26 of the toe post 22 and the two sidebands 24 through thecorresponding apertures 18 from the upper surface 14 of the solestructure and using the apertures 18 to obstructing the joining plugs 26from being pulled back.

According to one embodiment of the present invention, the strap 20 maybe made from plastic materials with elasticity, flexibility andtenacity, such as polyvinyl chloride (PVC) or thermoplastic polyesterelastomer (TPE) or the combination therefore, but not limited thereto.The strap 20 in its entirety may be made by injecting moldingtechnology. For example, the strap 20 may be made by injecting a thermalmolten plastic material into a lower mold and then laminating an uppermode onto the lower mode. The molten plastic material is cooled in themold to form the strap 20 with a desired shape.

According to one embodiment of the present invention, the sole structure12 may also be made from plastic materials with elasticity and tenacity,such as ethylene vinyl acetate (EVA), natural rubber, synthetic rubber,polyurethane (PU), polyvinyl chloride (PVC), thermal-plasticpolyurethane (TPU), thermal-plastic rubber (TPR) or polyethylene (PE),or the combination thereof, but not limited thereto. Preferably, thesole structure 12 is made of foamed plastic material, such as foamedEVA, foamed TPU or foamed rubber. Soles made from foamed plasticmaterial may have the advantages of light-weight for wearing comfort andenvironment-friendly for less plastic materials are used. According toan embodiment, the sole structure 12 may be made by the followingprocess. First, plastic raw materials are proportionally fed into anintensive mixer and are blended at a heated temperature thereby forminga molten blend of the plastic raw materials. After that, chemicaladditives such as foaming agent, cross-linking agent, activate agent,lubricating agent or other types of modifying agents are added into themixer and blended with the molten plastic raw materials to form ahomogenized mixture. The mixture is then transferred to a foam sheetmachine and being outputted into a stack of preliminary plastic foamsheet. The preliminary plastic foam sheet is then discharged and cutinto a plurality of sole sheets with designed shapes. Each of the solesheets is then loaded into a mold for vulcanization. Afterward, thevulcanized sole sheet is taken out from the mold and a finished solestructure is thereby obtained. According to an embodiment, the solestructure 12 may include a single layer or multiple laminated layers forproviding desired functionality, wearing comfort or wear-resistance.

Please refer to FIG. 3, which is an enlarged perspective view of thejoining plug 26 as shown in FIG. 2 according to an embodiment of thepresent invention. As shown in FIG. 3, the joining plug 26 may include apillar portion 262 and a blocking portion 264. One end of the pillarportion 262 is connected to the upper surface 266 of the blockingportion 264, while the other end of the pillar portion 262 is connectedto the toe post 22 or one of the sidebands 24 of the strap 20. Accordingto one embodiment, the pillar 262 may be cylinder-shaped, and theblocking portion 264 may be circular-plate shaped. The diameter of thepillar portion 262 is smaller than the diameter of the blocking portion264 to expose a portion of the upper surface 266 of the blocking portion264. When the pillar 262 is jointed at the center portion of the uppersurface 266 of the blocking portion 264, the joining plug 26 may have anupside-down T-shaped cross-sectional profile which corresponds to shapeof the aperture 18 (see FIG. 4). In this way, the joining plug 26 may beobstructed or latched in the aperture 18 thereby preventing thedisassembling of the sole structure 12 and the strap 20. One feature ofthe present invention is that, as shown in FIG. 3, the blocking portion264 of the joining plug 26 has a plurality of protrusions 268 disposedon the region of the upper surface 266 not covered by the pillar portion262. In some embodiments, the protrusions 268 may be evenly dispersed onthe upper surface 266 not covered by the pillar portion 262. In otherembodiments, the protrusions 268 may be arranged in a higher densitynear the pillar portion 262 and in a lower density as being distancedfrom the pillar portion 262, and vice versa. Optionally, the protrusions268 may be arranged into a certain pattern, such as a radial patterncentered at the pillar portion 262, a single ring or multiple concentricrings centered at the pillar portion 262. It some embodiment not shownin the diagram, a portion of the protrusions 268 may be joined to form asegment pattern or a contentious ring pattern surrounding the pillarportion 262. Other types of arrangements of the protrusions 268 are alsoapplicable for different design needs.

The entirety of the joining plug 26 (including the pillar portion 262,the blocking portion 264 and the protrusions 268) may be integrallyformed with other parts of the strap 20 by, for example, injectionmolding technology as previously illustrated. That is, no additionalmanufacturing steps or extra cost are needed for forming the joiningplug 26. The protrusions 268 may respectively have a cone shape, atriangle pyramid shape or a square pyramid shape, but not limitedthereto. Likewise, in other embodiments, the protrusions 268 mayrespectively have a cylinder shape or a prism shape. According to anembodiment, the ratio of the diameters of the pillar portion 262 and theblocking portion 264 may range from 1 to 1.5 and 1 to 3. For example,when the diameter of the pillar portion 262 is between 4 to 6millimeters (mm), the diameter of the blocking portion 264 is preferablybetween 6 to 18 millimeters. According to an embodiment, the diameter ofthe pillar portion 262 is 5 mm, the diameter of the blocking portion 264is 15 mm, and the height of the protrusions 268 protruding from theupper surface 266 of the blocking portion 264 may range from 0.5 mm to1.5 mm, preferably 1 mm.

Please refer to FIG. 4. The upper portion of FIG. 4 is a perspectivebottom view of the sole structure 12, and the lower portion of FIG. 4 isa cross-section view of the aperture 18 in the sole structure 12 alongthe line A-A′ shown in the upper portion of FIG. 4. As shown in FIG. 4,the aperture 18 comprises an passage hole 182 adjacent to the uppersurface 14 of the sole structure 12 and a receiving hole 184 connectedto the passage hole 182 and adjacent to the lower surface 16 of the solestructure 12. The passage hole 182 and the receiving hole 164 haveshapes respectively corresponding to the pillar portion 262 and theblocking portion 264 of the joining plug 26. For example, the passagehole 182 may be a cylinder hole, and the receiving hole may be acircular-plate hole. It is important that the diameter of the passagehole 182 is smaller than the diameter of the receiving hole 184 so as toform an engaging surface 186 near the terminal of the receiving hole 184connecting the passage hole 182. According to an embodiment, as shown inFIG. 4, the passage hole 182 is aligned to the center of the receivinghole 184. The aperture 18 has an upside-down T shaped cross-sectionalprofile corresponding to the shape of the joining plug 26 as shown inFIG. 3.

Please refer to FIG. 5 and FIG. 5A, which are cross-sectional diagramsshowing the assembly of a joining plug 16 and an aperture 18 of the solestructure 12. According to an embodiment, the assembly may be formed bypressing the joining plug 16 from the upper surface 14 of the solestructure 12 into the aperture 18 by the pliability of the joining plug16 and the sole structure 12. The upper surface 266 of the blockingportion 264 of the joining plug 26 would be stopped against the engagingsurface 186, thereby preventing the joining plug 26 from being pulledback through the aperture 18. Please refer to FIG. 5A, according to anembodiment when a force 270 pulling away from the upper surface 14 ofthe sole structure 12 is applied to the strap 20, for example, duringthe activity of the wearer, the joining plug 26 is pulled up, and theprotrusions 268 on the upper surface 266 would be at least partiallypressed into the sole structure 18 by the pliability of the solestructure 12. The contacting area of the upper surface 266 of theblocking portion 264 and the engaging surface 186 is thereforeincreased, and the friction between the upper surface 266 and theengaging surface 186 is further increased. Consequently, the possibilityof the disassembling between the joining plug 26 and the aperture 18 isfurther reduced and a more secured engagement between the strap 20 andthe sole structure 12 is achieved.

Please refer to Table 1 as shown below. Table 1 shows the experimentaldata of a pulling stress test of the assembly of the strap and the solestructure according to one embodiment of the present invention. Theexperiment is performed by the following steps. First, an assembly of astrap and a sole structure is provided. The sole structure is then heldon a base of a pulling testing machine and the end of the strap oppositeto the sole structure is clamped and pulled by a force vertical to theupper surface of the sole structure and away from the sole structure.The magnitude of the force is gradually increased and the reaction forcedetected by the clamped is also increased until a sudden drop of thereaction force is detected. The magnitude of the force is referred asthe maximum pulling stress. In Table 1, two sole structures, first solestructure (S1) and second sole structure (S2) are provided for thetesting. The first sole structure and the second sole structure maycomprise different materials and may comprise different elasticity orflexibility. Test 1, Test 2 and Test 3 are three different regions ofthe first sole structure the strap to be attached to. For example, Test1, Test 2 and Test 3 respectively correspond to the fore region 12 a andthe two side regions 12 b of the sole structure 12 as shown in FIG. 1.Similarly, Test 4, Test 5 and Test 6 respectively correspond to the foreregion 12 a and the two side regions 12 b of the second sole structurefor the strap to be attached to. In Table 1, column A shows test resultsof joining plugs without protrusions, and column B is average of columnA. Column C shows test results of joining plug including protrusions,and column D is average of column C. Column E shows the differencebetween column D and column B. Column F shows the percentage of theincrement of the tensile stress. It is shown in Table 1 that, assemblyof the strap and the sole structure having the joining plug withprotrusions may increase the maximum tensile stress by about 3kilograms. This amount of increment is about 20% to 30% of the assemblyof the strap and the sole structure without protrusions. According tothe experimental result, it is known that the joining plug withprotrusions is beneficial for assuring the assembly of the solestructure and the strap of a flip flop.

TABLE 1 A C without B with D E F protrusions average protrusions averageD-B E/B(%) S1 Test 1 11.83 10.50 14.79 13.71 3.21 30.57 Test 2 9.4912.40 Test 3 10.18 13.95 S2 Test 4 17.32 15.01 19.18 18.09 3.08 20.52Test 5 14.23 16.16 Test 6 13.49 18.94 Unit: kilogram (Kg)

According to another embodiment of the present invention, a constantstress magnitude, for example, 11.3 Kg may be applied to the assembly ofthe sole structure and the strap to examine the yield of the assembly.If no released reaction force is detected, the assembly is considered topass the test. Otherwise, if a released reaction force is detected, theassembly is considered to fail. Please refer to Table 1 again, thetesting result in column C (joining plug with protrusions) are alllarger than 11.3 Kg. That is, the assemblies would all pass the pullingstress test. However, test 2 and test 3 in column A (joining plugwithout protrusions) are smaller than 11.3 Kg and are considered fail.According to the above, it is obvious that the joining plug havingprotrusions are beneficial for securing the strap to the sole structure.The flip flop assembly including the joining plug having protrusions mayhave better yield.

Please refer to FIG. 6, which shows some modifications of the joiningplug according to some embodiments of the present invention. Theblocking portion 264 of the joining plug 26 may have various shapes,such as a square-plate shape as shown in the left portion of FIG. 6,oval-shape as shown in the middle portion of FIG. 6, or polygon-plateshape as shown in the right portion of FIG. 6, but not limited thereto.Similarly, although not shown in the diagram, it should be understoodthat the pillar portion 262 of the joining plug 26 may have variousshapes, such as square, oval or polygon, but not limited thereto.Furthermore, the shape of the aperture 18 may be adjusted according tothe shape of the blocking portion 264 and/or the pillar portion 262. Forexample, the receiving hole 184 may be a square opening corresponding toa square blocking portion 264.

Overall, the present invention provides a novel strap securing structureof a sandal which is able to prevent the disassembling of strap and solestructure occurring in conventional sandals and thereby providing betterwearing comfort and stability to the wearer. Furthermore, as theenvironmental awareness has already drawn a lot of attention in theindustry of footwear manufacturing, eco-friendly materials such asbio-degradable EVA or bio-degradable PVC have gradually taken the placeof conventional plastic materials for forming the sole structure. Asknown in the art, bio-degradable plastic materials are usually moreflexible than conventional plastic materials and therefore thedisassembling problem of a sandal made from bio-degradable plasticmaterials would be worse than made from conventional plastic materials.Advantageously, by using the trap securing component having a joiningplug with protrusions provided by the present invention, thedisassembling problem confronted when using bio-degradable plasticmaterials may be effectively eliminated.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. An article of sandal, comprising: a solestructure having an upper surface and a lower surface; an aperturepenetrating through the sole structure and exposing an engaging surfacebetween the upper surface and the lower surface; and a strap secured onthe upper surface of the sole structure, wherein the strap includes ajoining plug having a blocking portion and a pillar portion connected toa top surface of the blocking portion, wherein the top surface of theblocking portion has a plurality of protrusions that are in directcontact with the engaging surface of the sole structure.
 2. The articleof sandal according to claim 1, wherein the aperture comprises anpassage hole close to the upper surface and a receiving hole connectedto the passage hole and close to the lower surface of the solestructure, wherein the engaging surface is between the passage hole andthe receiving-hole portion of the aperture.
 3. The article of sandalaccording to claim 1, wherein the pillar portion is connected to acenter portion of the top surface of the blocking portion, wherein thejoining plug has an upside-down T shaped cross-sectional profile.
 4. Thearticle of sandal according to claim 1, wherein the aperture has anupside-down T shaped cross-sectional profile.
 5. The article of sandalaccording to claim 1, wherein the blocking portion of the joining plugis circular-plate shaped.
 6. The article of sandal according to claim 1,wherein the strap and the joining plug are formed in one integralstructure.
 7. The article of sandal according to claim 1, wherein thestrap is a Y-shaped strap comprising a toe post secured to a fore regionof the sole structure and two sidebands are joined at the toe post andrespectively secured to two side regions of the sole structure.
 8. Thearticle of sandal according to claim 1, wherein the protrusions areevenly distributed on the upper surface of the blocking portion exposedfrom the pillar portion.
 9. The article of sandal according to claim 1,wherein the sole comprises foamed ethylene vinyl acetate (EVA) or foamedrubber.
 10. The article of sandal according to claim 1, wherein thestrap comprises polyvinyl chloride (PVC).